Taking care of your lawn in South Florida can feel like a year-round job, and that’s because for most of homeowners, it is. One of the most effective ways to keep your lawn healthy and weed-free is to use pre-emergent herbicide—but timing and is everything. Let’s break down the best times to apply pre-emergents to make sure those pesky weeds don’t stand a chance.
Pre-emergent herbicides prevent weeds from growing
Pre-emergent herbicide is a type of lawn treatment designed to kills weeds as soon as they germinate. Instead of trying to fight weeds after they’ve already appeared (i.e. post-emergent herbicides), pre-emergents create a barrier in the soil that stops weeds before they get a chance to take over. It’s a proactive approach that can save a lot of trouble down the line.
When and how often to apply
Our tropical climate and short winters mean that weeds can pop up almost any time of year, so multiple applications of pree-emergent are generally ideal. South Florida gets a ton of rain, especially between June and September when we get about two-thirds of annual rainfall. These heavy rains can wash away pre-emergent, making it less effective.
An easy way to do this is to divide the maximum annual rate into two or three applications.
- Spring Application(s): The ideal time to apply pre-emergent in the spring is late February to early March, right before the weather starts warming up. Specifically, the soil temperature should exceed 70 for 3 consecutive days. This timing targets warm-season weeds like crabgrass, which begin to germinate as temperatures rise. We recommend splitting the spring app into two smaller applications to extend protection throughout the growing season.
- Fall Application: A second (or third) round of pre-emergent should be applied in late October through early November, or once soil temps drop below 70 for 3 consecutive days. This helps prevent winter weeds, such as poa annua and hairy bittercress, from taking over when temperatures start to cool off in South Florida.
Some rainfall after application is helpful, just not too much
When applying pre-emergent, it’s important to keep an eye on the forecast. Pre-emergents need to be watered in after application, so a light rainfall shortly after can be a great help. On the flip side, heavy rain can wash the herbicide away before it has a chance to work. Choosing a day with mild weather and planning to irrigate lightly afterwards is often the best approach.
A Few Tips for Success
- Apply Before Weeds Are Visible: Remember, pre-emergent herbicides won’t help with existing weeds. If you can already see weeds in your lawn, it’s too late for pre-emergent—you’ll need a post-emergent herbicide instead.
- Always Read the Label: Different products may have different application rates or timing suggestions, so be sure to read the label carefully.
- Don’t Disturb the Soil: After applying pre-emergent, try not to disturb the soil too much. Digging or aerating can break the barrier that the herbicide forms, reducing its effectiveness.
Always Keep Your Lawn a Step Ahead
Staying ahead of weeds with a well-timed pre-emergent application can make a big difference in how lush and healthy your lawn looks all year round. In South Florida, it’s all about taking advantage of those key windows—late winter and early fall—to make sure your lawn stays weed-free and thriving.
If you have any questions about lawn care or just need a bit of guidance, Floridist is always here to help keep your lawn at its best.